For organic electroluminescence (abbreviated as OLED) and related researches, pope et al., first discovered the electroluminescence phenomenon of an organic compound, monocrystalline anthracene in 1963. In 1987, the Kodak Company of U.S. fabricated an amorphous film-type device using a method for the evaporation of organic small molecules, which reduces the drive voltage to 20 V or lower. Such devices can be widely used in flat panel displays and surface light sources due to having advantages of being ultrathin, all solid state, self-illumination, a high brightness, a wide viewing angle, a fast response speed, a ow drive voltage, a low power consumption, a bright colour, a high contrast ratio, a simple technological process, good temperature characteristics, being capable of achieving a flexible display, etc., and therefore has been widely studied, developed and used.
After 20 years of development, organic EL materials have fully realized red, blue and green luminescence, and the application field has also been extended to areas such as macromolecules and metal complexes from small molecules. In recent years, the organic electroluminescence display technology has become mature, and some products have entered the market; however, in the process of industrialization, there are still many problems to be solved urgently, particularly various organic materials for manufacturing devices, there are still many problems that have not been solved yet, e.g., the carrier injection, transmission performance, material luminous performance, service life, and colour purity thereof, the match between the various materials and between various electrodes. Especially, the luminous efficiency and service life of light-emitting devices have not met the practical requirements yet, which greatly limits the development of the OLED technology. However, the use of triplet state-luminescent metal complex phosphorescent materials provides a high luminous efficiency, wherein green and red light materials thereof have met the service requirements, but the special electronic structure characteristics of the metal complex results in that the blue light material cannot meet the service requirements.
The appearance of a thermally activated delayed fluorescent material between fluorescence and phosphorescence greatly increases the luminous efficiency of the fluorescent material, which almost achieves the luminous efficiency of a phosphorescent material, and makes up for the deficiency of the phosphorescent blue light material, while avoiding the use of noble rare metals, greatly reducing the material cost. However, the thermally activated delayed fluorescent materials that have been reported can be used for preparing OLED devices only by a doping method due to the presence of an aggregation-caused quenching effect in the solid state. Therefore, it is an approach to solve the above-mentioned problems by developing a thermally activated delayed fluorescent material having an aggregation-induced emission effect in the solid state.